An impeller pump includes an impeller running in a pumping chamber within a housing of the pump. The impeller is mounted on a shaft to which a drive pulley is coupled. An impeller pump performs best when a gap between an interior wall of the pumping chamber and the impeller is as small as possible. To achieve high efficiencies, this gap should be constant over the depth of the impeller.
Metal pump housings are commonly used for impeller pumps. One advantage of a metal housing is its structural integrity. Strong lateral forces can be applied to the drive pulley before the shaft is displaced or bent, which results in performance losses or destruction of the pump. For marine applications, the metal pump housing typically decomposes over time when aggressive fluids (e.g., salt water or water with a high chlorine content) are pumped.
Composite pump housings have been used due to their ability to withstand a wider range of aggressive fluids, especially chlorine water, while being more cost effective than precious metals. Additionally, whenever the weight of the pump is important, the composite pump housings have clear advantages over their metal counterparts. Disadvantages of the composite pump housings include their inability to compensate shear forces. Strong lateral forces applied to the drive pulley can decrease the performance of the pump more rapidly or even destroy the pump more easily as compared to the metal pump housings. Attempts to overcome this limitation of the composite pump housings include increasing wall thicknesses throughout the pump housing and/or reinforcing the composite pump housing. The wall thicknesses required for the strong forces applied to the shaft in modem applications would result in undesirable pump dimensions. However, reinforcing the pump housing by, for example, wood or metal inserts, can result in cracking at the interfaces of the reinforcement. Additionally, either solution is less cost effective.